Illumination System Based on Active and Passive Illumination Devices

ABSTRACT

Illumination systems are described for illuminating a target area, e.g., a floor of a room, using active illumination devices in optical communication with passive illumination devices. The active and passive illumination devices of the illumination system are configured and arranged relative to each other in a variety of ways so a variety of intensity distributions can be provided by the illumination system. Such illumination system is implemented to provide light for particular lighting applications, including office lighting, garage lighting, or cabinet lighting.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/675,642, filed Aug. 11, 2017, which is a continuation of U.S.application Ser. No. 14/766,644, filed Aug. 7, 2015, which is a U.S.National Stage of International Application No. PCT/US2014/015255, filedFeb. 7, 2014, which claims benefit under 35 U.S.C. § 119(e)(1) of U.S.Provisional Application No. 61/762,817, filed on Feb. 8, 2013, which areincorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to illumination systems that use activeand passive illumination devices.

BACKGROUND

Light sources are used in a variety of applications, such as providinggeneral illumination and providing light for electronic displays (e.g.,LCDs). Historically, incandescent light sources have been widely usedfor general illumination purposes. Incandescent light sources producelight by heating a filament wire to a high temperature until it glows.The hot filament is protected from oxidation in the air with a glassenclosure that is filled with inert gas or evacuated. Incandescent lightsources are gradually being replaced in many applications by other typesof electric lights, such as fluorescent lamps, compact fluorescent lamps(CFL), cold cathode fluorescent lamps (CCFL), high-intensity dischargelamps, and light-emitting diodes (LEDs).

SUMMARY

The present disclosure relates to illumination systems configured toilluminate a target area, e.g., a floor of a room, using activeillumination devices in optical communication with passive illuminationdevices. Active illumination devices serve to direct light both to thetarget area and to the passive illumination devices. Rather than emitillumination themselves, the passive illumination devices serve toredirect illumination received from the active illumination devicestowards the target area. The active and passive illumination devices ofthe illumination system can be configured and arranged relative to eachother in a variety of ways so a variety of intensity distributions canbe provided by the illumination system. Such illumination systems can beconfigured to provide light for particular lighting applications,including office lighting, garage lighting, or cabinet lighting, forinstance.

Various aspects of the invention are summarized as follows.

In general, in a first aspect, the invention features an illuminationsystem that includes multiple active illumination devices spaced apartfrom each other and from a target surface, each of the activeillumination devices comprising one or more light emitting elements(LEEs) and first redirecting optics and one or more passive illuminationdevices distributed between and in optical communication with the activeillumination devices, each of the passive illumination devicescomprising one or more second redirecting optics. For each of the activeillumination devices, the first redirecting optics are arranged andconfigured to redirect light emitted by the one or more LEEs in a firstangular range as (i) first direct light in a second angular range and(ii) indirect light in a third angular range, such that a prevalentdirection of the first direct light in the second angular range istowards an associated direct portion of the target surface, and aprevalent direction of the indirect light in the third angular range isdirected towards one or more of the passive illumination devices. Foreach of the one or more passive illumination devices, the secondredirecting optics are arranged and configured to redirect the indirectlight received from one or more of the active illumination devices inone or more of the third angular ranges, and to provide the redirectedlight as second direct light in one or more fourth angular ranges, suchthat a prevalent direction of the second direct light in the one or morefourth angular ranges is towards one or more associated indirectportions of the target surface.

Implementations of the first aspect may include one or more of thefollowing features. For example, the active illumination devices and theone or more passive illumination devices may be spaced-apart from oneanother and from the target surface such that corresponding first andsecond direct light combine in a desired illumination distribution ofthe target surface. Divergences of the second and third angular rangesmay be smaller than a divergence of the first angular range.

In general, in another aspect, the invention features an illuminationsystem that includes at least one active illumination device, eachactive illumination device comprising at least one light emittingelement and an optical element arranged to receive light from the atleast one light emitting element and to direct illumination from the atleast one light emitting element in at least two discrete illuminationranges in a cross-sectional plane, and a support for attaching theactive illumination device to a ceiling and at least one passiveillumination device, each active illumination device comprising areflector and a support for attaching the passive illumination device tothe ceiling. The reflector is configured such that when both the activeand passive illumination devices are attached to the ceiling and spacedapart a pre-established distance from each other, the reflector receiveslight directed by the optical element into one of the discrete angularranges and directs the received light toward a target surface.

Implementations of this aspect may include one or more of the followingfeatures. For example, when both the active and passive illuminationdevices are attached to the ceiling, the corresponding supports of theat least one active illumination device and at least one passiveillumination device may be configured to position the optical element ofthe at least one active illumination device at a height further from theceiling than the reflector of the at least one passive illuminationdevice. When the at least one passive illumination device is attached tothe ceiling, the support of the at least one passive illumination devicemay position the reflector of the passive illumination device atsubstantially the same height as the ceiling. When the at least onepassive illumination device is attached to the ceiling, the support ofthe at least one passive illumination device may position the reflectorof the passive illumination device at a height below the ceiling.

When the at least one active device is attached to the ceiling, lightpropagating in two of the at least two discrete angular ranges maypropagate towards the ceiling.

When both the active and passive illumination devices are attached tothe ceiling, both the active and passive illumination devices may directlight towards the target surface. When both the active and passiveillumination devices are attached to the ceiling, light from the atleast one active illumination device and an adjacent one of the passiveillumination devices can overlap on the target surface.

In certain implementations, when both the active and passiveillumination devices are attached to the ceiling, light from theillumination system incident on the target surface does not exceed aglancing angle of 40° with respect to an axis perpendicular to theceiling.

The at least one illumination device may be elongated in a directionperpendicular to the cross-sectional plane.

The at least one active illumination device may have a plane of symmetryorthogonal to the cross-sectional plane.

The at least one active illumination device may include a light guideconfigured to guide light from the at least one light emitting device tothe optical element.

The optical element of the at least one active illumination device mayinclude an interface configured to reflect at least some of the lightfrom the at least one light emitting device into two of the discreteangular ranges. The interface may be configured to transmit at leastsome of the light from the at least one light emitting element into atleast one of the discrete angular ranges.

The at least one active illumination device may include a reflectorpositioned to reflect light from the optical element.

The at least one light emitting element can be a light emitting diode.

The reflector of the at least one passive illumination device may be acurved reflector (e.g., a convex reflector). In some implementations,the reflector of the at least one passive illumination element is aFresnel reflector.

When the active and passive illumination devices are attached to theceiling and spaced apart a pre-established distance from each other, thereflector of the passive illumination device may receive light from twoactive illumination devices on opposing sides of the passiveillumination device.

When the active and passive illumination devices are attached to theceiling and spaced apart a pre-established distance from each other, theat least one active illumination device can be configured to directlight to passive illumination devices on opposing sides of the activeillumination device.

Among other advantages, the disclosed illumination systems may offersubstantial design flexibility in the illumination profile delivered toa target area. For example, illumination systems include opticalcomponents (e.g., reflecting, refracting, scattering, and/or diffractingelements) that can be used to direct light from a light emitting elementinto discrete angular ranges. In this way, the systems may deliver lightfrom a point-like light source (e.g., a light emitting diode) to anextended target surface such that the light is incident only overcertain angular ranges. For instance, the light may be incident atangles close to normal incidence on a planar target area, therebyreducing or eliminating glare.

Additionally, or alternatively, the illumination systems may provideefficient distribution of light to a relatively large target area fromsmall, but intense, light emitting elements. For example, the systemsmay include passive illumination devices that are installed remotelyfrom active illumination devices and re-direct light from the activeillumination devices towards the target area. In this way, the passiveillumination devices may also serve to ensure that light at the targetarea is incident at angles that don't contribute to glare.

The term “light-emitting element” (LEE), also referred to as a lightemitter, is used herein to refer to devices that emit radiation in oneor more regions of the electromagnetic spectrum from among the visibleregion, the near infrared region and/or the ultraviolet region, whenactivated. Activation of an LEE can be achieved by applying a potentialdifference across components of the LEE and/or passing a current throughcomponents of the LEE, for example. A light-emitting element can havemonochromatic, quasi-monochromatic, polychromatic or broadband spectralemission characteristics. Examples of light-emitting elements includesemiconductor, organic, polymer/polymeric light-emitting diodes (e.g.,organic light-emitting diodes, OLEDs), other monochromatic,quasi-monochromatic or other light-emitting elements. Furthermore, theterm light-emitting element is used to refer to the specific device thatemits the radiation, for example a LED die, and can equally be used torefer to a combination of the specific device that emits the radiation(e.g., a LED die) together with a housing or package within which thespecific device or devices are placed (e.g., an LED die packaged with aphosphor). Examples of light emitting elements include also lasers andmore specifically semiconductor lasers, such as vertical cavity surfaceemitting lasers (VCSELs) and edge emitting lasers. Further examplesinclude superluminescent diodes and other superluminescent devices.

As used herein, providing light in an “angular range” refers toproviding light that propagates in a prevalent direction and has adivergence with respect to the propagation direction. In this context,the term “prevalent direction of propagation” refers to a directionalong which a portion of an intensity distribution of the propagatinglight has a maximum. For example, the prevalent direction of propagationassociated with the angular range can be an orientation of a lobe of theintensity distribution. Also in this context, the term “divergence”refers to a solid angle outside of which the intensity distribution ofthe propagating light drops below a predefined fraction of a maximum ofthe intensity distribution. For example, the divergence associated withthe angular range can be the width of the lobe of the intensitydistribution. The predefined fraction can be 10%, 5%, 1%, or othervalues, depending on the lighting application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an example of an illumination system including activeillumination devices and passive illumination devices.

FIG. 1B shows an example of an intensity profile of an activeillumination device used in the illumination system of FIG. 1A.

FIG. 1C shows another example of an intensity profile of an activeillumination device used in the illumination system of FIG. 1A.

FIGS. 2A-2G show aspects of various embodiments of active illuminationdevices.

FIG. 3 shows an example of a solid embodiment of an active illuminationdevice.

FIG. 4 shows an example of a hollow embodiment of an active illuminationdevice.

FIG. 5 shows another example of an active illumination device.

FIG. 6 shows another example of an active illumination device.

FIG. 7 shows another example of an active illumination device.

FIG. 8 shows another example of an active illumination device.

FIG. 9 shows an example of a passive illumination device.

FIG. 10 shows another example of a passive illumination device.

Reference numbers and designations in the various drawings indicateexemplary aspects of implementations of particular features of thepresent disclosure. Like reference numbers indicate like elements.

DETAILED DESCRIPTION

The present disclosure relates to illumination systems configured toilluminate a target area, e.g., a floor of a room, a garage, etc., usingactive illumination devices in optical communication with passiveillumination devices. The active illumination devices include lightemitting elements (LEEs, such as, e.g., light emitting diodes, LEDs) andredirecting optics that are configured to provide direct illumination ofthe target area and indirect illumination towards a background area,e.g., away from the target area. In general, “direct” illuminationrefers to illumination that propagates directly from a luminaire to thetarget area, while “indirect” illumination refers to illumination thatreflects (e.g., diffusely reflects) from another surface, often aceiling, before illuminating the target area. In some implementations,the active illumination devices are configured to allow interdependentas well as independent control of the direct and indirect illuminationsby a user. The passive illumination devices include redirecting optics(but no light emitting elements). The passive illumination devices arearranged relative to the active illumination devices to redirect,towards the target area, the indirect illumination provided by theactive illumination devices. Example systems include at least one activeillumination device and at least one passive illumination device.

(i) Illumination Systems Including Active and Passive IlluminationDevices

FIG. 1A schematically illustrates an illumination system 100 suspendedfrom a ceiling 180 of a room and configured to illuminate the room. ACartesian coordinate system is shown for reference. The x-y plane isparallel to the ceiling 180 and a floor 190, while the z-axis isperpendicular to both. As illustrated, the illumination system 100includes four active illumination devices 150 in optical communicationwith three passive illumination devices 170, although, more generally,illumination systems can include more or fewer active and passiveillumination devices. In some implementations, the active illuminationdevices 150 and the passive illumination devices 170 are elongated alongthe y-axis, perpendicular to the page.

In the example illustrated in FIG. 1A, the floor 190 is the target areafor illumination system 100, and the background area is the ceiling 180.Here, the active illumination devices 150 include supports 108 thatattach the illumination device thereto and suspend the activeillumination devices a height H therefrom. In some implementations, thesupports 108 can be wires, rods, or combinations thereof.

In general, the active illumination devices 150 include one or morelight emitting elements (LEEs, such as, e.g., light emitting diodes(LEDs)) configured to emit light, and redirecting optics coupled withthe LEEs. Depending on the embodiment, the system is configured toredirect the emitted light as output light in one or more direct angularranges 152, 152′ and indirect angular ranges 162, 162′. In this manner,the active illumination devices 150 are configured to provide directillumination of the target area (in accordance with the one or moredirect angular ranges 152, 152′), and indirect illumination towards theceiling 180 (as illustrated by the indirect angular distributions 162,162′). While the target area in FIG. 1A is the floor 190, more generallythe target area can be a workspace on a desk, a floor or other targetarea.

The passive illumination devices 170 include supports (e.g., rods,wires, or combinations thereof) which attach the passive illuminationdevices to the ceiling 180 and suspend them a height h therefrom. Thesupport can have an appropriate length to support the passiveillumination device 170 at a specified distance (h≠0) from the ceiling.In general, the passive illumination devices are positioned to receiveillumination directed by the active illumination devices into ranges 162and 162′, so h depends on the design and position of the activeillumination devices 150. In general, h<H. In certain embodiments, H-his in a range from about six inches to about three feet. In someimplementations, the passive illumination devices 170 can be supporteddirectly from the ceiling 180 or integrated in the ceiling 180, withoutthe use of wires or rods (h=0).

The passive illumination devices 170 include redirecting optics (notshown in FIG. 1A). As suggested by their name, the passive illuminationdevices 170 do not include LEEs and thus do not generate lightthemselves. The passive illumination devices 170 are arranged relativeto the active illumination devices 150 to receive light emitted by theactive illumination devices 150. The redirecting optics of the passiveillumination devices 170 are arranged to redirect, towards the targetarea, the indirect illumination received from the active illuminationdevices 150 in the indirect angular ranges 162, 162′. The redirectingoptics redirect the light from active illumination devices 170 inangular ranges 172, 172′. In this manner, the passive illuminationdevices 170 provide direct illumination of the target area (in the formof redirected light in the direct angular ranges 172, 172′). Examples ofpassive illumination devices 170 are described below in connection withFIGS. 9 and 10.

In general, the illumination system 100 is configured to provide aparticular light intensity distribution on a target surface, subject togiven constraints. In FIG. 1A, the illumination system 100 may beconfigured to substantially uniformly illuminate the floor 190 (e.g., toobtain approximately 10% overlap between each of adjacent direct angularranges 152, 172, 172′ and 152′ at the floor level, thereby providingcontinuous illumination of the floor with little variation inintensity), and to be in conformance with glare standards (e.g., lightredirected towards the floor 190 in any of the direct angular ranges152, 152′, 172 and 172′ does not exceed a glancing angle of 40° withrespect to the z-axis.) In addition to maintaining glare standards, theillumination system 100 may be configured such that a distance D (seeFIG. 1A) between nearest active illumination devices 150 to be largerthan a distance between conventional luminaires required in conventionalillumination systems that do not employ passive illumination devices170.

Such configurations of the illumination system 100 can be implemented byselecting appropriate combinations of system parameters including (i)direct angular ranges 152, 152′ of direct light output by the activeillumination devices 150; (ii) indirect angular ranges 162, 162′ ofindirect light output by the active illumination devices 150 relative tothe direct angular ranges 172, 172′ of light redirected by the passiveillumination devices 170; (iii) distance D between nearest activeillumination devices 150, e.g., about 6 ft or more, about 10 ft or more,about 15 ft or more, about 24 ft; (iv) distance d between adjacentactive illumination devices 150 and passive illumination devices 170,such that D>d, e.g., about 3 ft or more, about 5 ft or more about 8 ftor more, about 10 ft or more, about 12 ft; (v) distance H from theceiling 180 to an effective center of the active illumination devices150, e.g., H=3 ft; (vi) distance h from the ceiling 180 to an effectivecenter of the passive illumination devices 170, such that H≥h=0 or 3 ft,for instance.

In general, these parameters are selected based on the desiredillumination intensity and illumination directions desired at the targetarea. For instance, where a larger range of incident angles (relative tothe z-axis) are desired, greater separation between the passive andactive illumination devices is permissible.

FIG. 1B shows, for the x-z plane, an example light intensity profile 151of an active illumination device 150. Here, the z-axis corresponds tothe axis from 0° to 180°, where 0° is in the direction of the floor. Theintensity profile 151 includes four lobes 152 a, 152 b, 162 a, and 162b. Depending on the embodiment, a distinction between lobes 152 a and152 b may be notional as both may be superimposed, for example, andappear indistinguishable from each other. The result may be similar towhat is described with respect to FIG. 1C. Here, active illuminationdevices 150 are configured to direct substantially all of the indirect(background) light 162 a, 162 b into a range of polar angles between−90° and −110°, and between +90° and +110° in a cross-sectional plane(x-z) of the active illumination devices 150. The active illuminationdevices 150 are also configured to direct substantially all of theforward (e.g., direct) light into a pair of narrow lobes 152 a, 152 bhaving a range of polar angles having maximum intensity at −50° and +50°in the x-z cross-sectional plane, respectively. Lobes 152 a, 152 b ofthe light intensity profile 151 correspond to the direct angular ranges152, 152′ shown in FIG. 1A and lobes 162 a, 162 b correspond to indirectangular ranges 162, 162′.

FIG. 1C shows another example light intensity profile 153 from an activeillumination device 150. Here, intensity profile 153 includes lobes 162a and 162 b having maximal intensity at −100° and +100°, respectively.These lobes correspond to indirect illumination. Intensity profile 153also includes a single lobe 154 in the forward direction, providingillumination in an angular range from about −60° to +60°.

In general, light emitting in the forward direction (e.g., lobes 152 a,152 b, or lobe 154) may be within a ranged between about −50° and about+50° (e.g., from about −60° and about +60°, from about −70° and about+70°) in order to reduce glare from the illumination system.

As described in detail below, composition and geometry of components ofthe active illumination devices 150 affect the light intensity profile151 and may be selected to provide direct and indirect illumination intoranges having varying angular width and direction. Examples of activeillumination devices follow.

(ii) Active Illumination Devices

FIG. 2A shows an example of an active illumination device 200. Theactive illumination device 200 includes a mount 210 having a pluralityof LEEs 212 distributed along a first surface 210 a of the mount 210.The active illumination device 200 includes an optical coupler 220, alight guide 230, and an optical extractor 240. Light emitted by the LEEs212 couples into the light guide 230 (either directly or upon reflectionby surfaces 221 and 222 of coupler 220) and is guided by the light guideto optical extractor 240. In optical extractor 240, the light isincident on surfaces 242 and 244, where part of the light is reflectedand part of the light is transmitted. The transmitted light exits activeillumination device 200 into angular range 252 adjusted (typicallyenlarged) by the relative refractive index. The reflected light exitsthe optical extractor through surfaces 246 and 248. The activeillumination device 200 is an example of an active illumination device150 (see FIG. 1A), where the direct illumination corresponds to lightoutput in the angular ranges 152, 152′, and indirect illuminationcorresponds to light output in the angular ranges 142, 142′. Anotheractive illumination device can be configured to output light in forwarddirection in an angular range qualitatively similar to angular range 154of FIG. 1C, for example

As shorthand, the positive z-direction is referred to herein as the“forward” direction and the negative z-direction is the “backward”direction. Sections through the illumination device parallel to the x-zplane are referred to as the “cross-section” or “cross-sectional plane”of the illumination device. In this example, active illumination device200 extends along the y-direction, so this direction is referred to asthe “longitudinal” direction of the active illumination device. Lastly,implementations of active illumination devices can have a plane ofsymmetry parallel to the y-z plane. This is referred to as the “symmetryplane” of the active illumination device.

Mount 210, light guide 230, and optical extractor 240 extend a length Lalong the y-direction, so that the luminaire module is an elongatedluminaire module with an elongation of L that may be about parallel to awall of a room (e.g., a ceiling of the room). Generally, L can vary asdesired. Typically, L is in a range from about 1 cm to about 200 cm(e.g., 20 cm or more, 30 cm or more, 40 cm or more, 50 cm or more, 60 cmor more, 70 cm or more, 80 cm or more, 100 cm or more, 125 cm or more,or, 150 cm or more).

The number of LEEs 212 on the mount 210 will generally depend, interalia, on the length L, where more LEEs may be used for longer luminairemodules. In some implementations, the plurality of LEEs 212 can includebetween 10 and 1,000 LEEs (e.g., about 50 LEEs, about 100 LEEs, about200 LEEs, about 500 LEEs). Generally, the density of LEEs (e.g., numberof LEEs per unit length) will also depend on the nominal power of theLEEs and illuminance desired from the luminaire module. For example, arelatively high density of LEEs can be used in applications where highilluminance is desired or where low power LEEs are used. In someimplementations, the active illumination device 200 has an LEE densityalong its length of 0.1 LEE per centimeter or more (e.g., 0.2 percentimeter or more, 0.5 per centimeter or more, 1 per centimeter ormore, 2 per centimeter or more). In implementations, LEEs can be evenlyspaced along the length, L, of the luminaire module. In someimplementations, a heat-sink 205 can be attached to the mount 210 toextract heat emitted by the plurality of LEEs 212. The heat-sink 205 canbe disposed on a surface of the mount 210 opposing the side of the mount210 on which the LEEs 212 are disposed.

Optical coupler 220 includes one or more solid pieces of transparentoptical material (e.g., a glass material or a transparent organicplastic, such as polycarbonate or acrylic) having surfaces 221 and 222positioned to reflect light from the LEEs 212 towards the light guide230. In general, surfaces 221 and 222 are shaped to collect and at leastpartially collimate light emitted from the LEEs. In the x-zcross-sectional plane, surfaces 221 and 222 can be straight or curved.Examples of curved surfaces include surfaces having a constant radius ofcurvature, parabolic or hyperbolic shapes. In some implementations,surfaces 221 and 222 are coated with a highly reflective material (e.g.,a reflective metal, such as aluminum or silver), to provide a highlyreflective optical interface. The cross-sectional profile of opticalcoupler 220 can be uniform along the length L of active illuminationdevice 200. Alternatively, the cross-sectional profile can vary. Forexample, surfaces 221 and/or 222 can be curved out of the x-z plane.

The surface of optical coupler 220 adjacent upper edge of light guide230 is optically coupled to edge 231. In some embodiments, the surfacesof the interface are attached using a material that substantiallymatches the refractive index of the material forming the optical coupler220 or light guide 230 or both. For example, optical coupler 220 can beaffixed to light guide 230 using an index matching fluid, grease, oradhesive. In some implementations, optical coupler 220 is fused to lightguide 230 or they are integrally formed from a single piece of material(e.g., coupler and light guide may be monolithic and may be made of asolid transparent optical material).

In general, optical couplers 220 are designed to restrict the angularrange of light entering the light guide 230 (e.g., to within +/−40degrees) so that at least a substantial amount of the light is coupledinto spatial modes in the light guide 230 that undergoes TIR at the sidesurfaces of the light guide. The example light guide 230 has a uniformthickness T, which is the distance separating two planar opposingsurfaces of the light guide. Generally, T is sufficiently large so thelight guide has an aperture at an upper edge 231 sufficiently large toapproximately match (or exceed) the aperture of optical coupler 220. Insome implementations, T is in a range from about 0.05 cm to about 2 cm(e.g., about 0.1 cm or more, about 0.2 cm or more, about 0.5 cm or more,about 0.8 cm or more, about 1 cm or more, about 1.5 cm or more).Depending on the implementation, the narrower the light guide the betterit may spatially mix light. A narrow light guide also provides a narrowexit aperture. As such light emitted from the light guide can beconsidered to resemble the light emitted from a one-dimensional linearlight source, also referred to as an elongate virtual filament.

Light guide 230 is formed from a piece of transparent material (e.g.,glass material such as BK7, fused silica or quartz glass, or atransparent organic plastic, such as polycarbonate or acrylic) that canbe the same or different from the material forming optical couplers 220.The example light guide 230 extends length L in the y-direction, has auniform thickness T in the x-direction, and a uniform depth Δ in thez-direction. The dimensions Δ and T are generally selected based on thedesired optical properties of the light guide and/or the direct/indirectintensity distribution. During operation, light coupled into the lightguide 230 from optical coupler 220 (depicted by rays 252 or angularrange 252) reflects off the planar surfaces of the light guide by totalinternal reflection and spatially mixes within the light guide. Themixing can help achieve illuminance and/or color uniformity at the loweredge 232 of the light guide 230 at optical extractor 240. The depth, Δ,of light guide 230 can be selected to achieve adequate uniformity at theexit aperture (i.e., at end 232) of the light guide. In someimplementations, Δ is in a range from about 1 cm to about 20 cm (e.g., 2cm or more, 4 cm or more, 6 cm or more, 8 cm or more, 10 cm or more, 12cm or more).

While optical coupler 220 and light guide 230 are formed from solidpieces of transparent optical material, hollow structures are alsopossible. For example, the optical coupler 220 or the light guide 230 orboth may be hollow with reflective inner surfaces rather than beingsolid. As such material cost can be reduced and absorption in the lightguide avoided. A number of specular reflective materials may be suitablefor this purpose including materials such as 3M Vikuiti™ or Miro IV™sheet from Alanod Corporation where greater than 90% of the incidentlight would be efficiently guided to the optical extractor.

The surface of optical extractor 240 adjacent to the lower edge 232 oflight guide 230 is optically coupled to edge 232. For example, opticalextractor 240 can be affixed to light guide 230 using an index matchingfluid, grease, or adhesive. In some implementations, optical extractor240 is fused to light guide 230 or they are integrally formed from asingle piece of material.

Optical extractor 240 is also composed of a solid piece of transparentoptical material (e.g., a glass material or a transparent organicplastic, such as polycarbonate or acrylic) that can be the same as ordifferent from the material forming light guide 230. In the exampleimplementation shown in FIG. 2A, the piece of dielectric materialincludes redirecting (e.g., flat) surfaces 242 and 244 and curvedsurfaces 246 and 248. The flat surfaces 242 and 244 represent first andsecond portions of a redirecting surface 243, while the curved surfaces246 and 248 represent first and second output surfaces of the activeillumination device 200.

Surfaces 242 and 244 are coated with a highly reflective material (e.g.,a highly reflective metal, such as aluminum or silver) over which aprotective coating may be disposed. Thus, surfaces 242 and 244 provide ahighly reflective optical interface for light entering an input end ofthe optical extractor from light guide 230. The surfaces 242 and 244include portions that are transparent to the light entering at the inputend of the optical extractor. For example, these portions can beuncoated regions or discontinuities (e.g., slots, slits, apertures) ofthe surfaces 242 and 244. The transmitted light exits the opticalextractor 240 through surfaces 242 and 244 in angular ranges 152 and152′, respectively. The transmitted light also may also be refracted,

In the x-z cross-sectional plane, the lines corresponding to surfaces242 and 244 can have the same length and form an apex or vertex 241,e.g. a v-shape that meets at the apex 241. In general, the includedangle (e.g., the smallest included angle between the surfaces 244 and242) of the redirecting surfaces 242, 244 can vary as desired. Forexample, in some implementations, the included angle can be relativelysmall (e.g., from 30° to 60°). In certain implementations, the includedangle is in a range from 60° to 120° (e.g., about 90°). The includedangle can also be relatively large (e.g., in a range from 120° to 150°or more).

In the example implementation shown in FIG. 2A, the output surfaces ofthe optical extractor 246 and 248 are curved with a constant radius ofcurvature that is the same for both. Accordingly, active illuminationdevice 200 has a plane of symmetry intersecting apex 241 parallel to they-z plane. Because surfaces 246 and 248 are curved, they may serve tofocus light (e.g., reduce the amount of divergence of the light)reflected by redirecting surfaces 242 and 244.

In general, the geometry of the optical extractor 240 plays a role inshaping the lobes of light emitted by the active illumination device.For example, the smaller the angle at apex 241, the lower the angle ofincidence the reflected light will have and the smaller the angle of itsdeflection. Accordingly, the vertex angle can be used to provide thedesired direction of the lobes of indirect light emitted by the activeillumination device.

The emission spectrum of the active illumination device 200 correspondsto the emission spectrum of the LEEs 212. However, in someimplementations, a wavelength-conversion material may be positioned inthe luminaire module, for example remote from the LEEs, so that thewavelength spectrum of the luminaire module is dependent both on theemission spectrum of the LEEs and the composition of thewavelength-conversion material. In general, a wavelength-conversionmaterial can be placed in a variety of different locations in activeillumination device 200. For example, a wavelength-conversion materialmay be disposed proximate the LEEs 212, adjacent surfaces 242 and 244 ofoptical extractor 240, on the exit surfaces 246 and 248 of opticalextractor 240, placed at a distance from the exit surfaces 246 and 248and/or at other locations.

In some embodiments, a layer of wavelength-conversion material may beattached to light guide 230 held in place via a suitable supportstructure (not illustrated), disposed within the extractor (also notillustrated) or otherwise arranged, for example. Wavelength-conversionmaterial that is disposed within the extractor may be configured as ashell or other object and disposed within a notional area that iscircumscribed by R/n or even smaller R*(1+n²)^((−1/2)), where R is theradius of curvature of the light-exit surfaces (246 and 248 in FIG. 2)of the extractor and n is the index of refraction of the portion of theextractor that is opposite of the wavelength-conversion material asviewed from the reflective surfaces (242 and 244 in FIG. 2A). Thesupport structure may be transparent self-supporting structure. Thelight-converting material diffuses light as it converts the wavelengths,provides mixing of the light and can help uniformly illuminate tertiaryreflectors (not shown in FIG. 2A).

As noted previously, the geometry of optical extractor 240 plays animportant role in shaping the light emitted by the active illuminationdevice. For instance, the shape of surfaces 242 and 244 may vary inaccordance with the desired emission. While surfaces 242 and 244 aredepicted as planar surfaces, other shapes are also possible. Forexample, these surfaces can be curved or faceted. Curved redirectingsurfaces 242 and 244 can be used to narrow or widen the beam. Dependingof the divergence of the angular range of the light that is received atthe input end of the optical extractor, concave reflective surfaces 242,244 can narrow the light intensity distribution output by the opticalextractor 240, while convex reflective surfaces 242, 244 can widen thelight intensity distribution output by the optical extractor 240. Assuch, suitably configured redirecting surfaces 242, 244 may introduceconvergence or divergence into the light. Such surfaces can have aconstant radius of curvature, can be parabolic, hyperbolic, or have someother curvature.

FIGS. 2B and 2D show redirecting surfaces 243-b and 243-d having an apex241 that separates the curved redirecting surface 242, 244. It should benoted that the apex 241 of the redirecting surface can be a roundedvertex with a non-zero radius of curvature. Here, the redirectingsurface 242, 244 have arcuate shapes in the cross-sectional planesubstantially perpendicular to the longitudinal dimension of the activeillumination device 200. For example, the first and second portions ofthe redirecting surface 242, 244 can be parabolic, hyperbolic, and/orcan have constant curvatures different from each other. Moreover,curvatures of the first and second portions of the redirecting surface242, 244 can be both negative (e.g., convex with respect to a directionof propagation of light from the input end of the extractor to theredirecting surface), can be both positive (e.g., concave with respectto the propagation direction), or one can be positive (convex) and theother one can be negative (concave).

FIG. 2E shows a redirecting surface 243-e shaped as an arc of a circle,ellipse, parabola or other curve. In this case, the first and secondportions of the redirecting surface 242, 244 represent first and secondportions of the arc of the circle. The curvature of the redirectingsurface 243 is negative (e.g., convex with respect to a direction ofpropagation of light from the input end of the extractor to theredirecting surface 243).

FIG. 2C shows a redirecting surface 243-c that includes faceted surfaces242, 244. Here, the surfaces meet at apex 241. Additionally, the facetsforming surface 242 meet at an apex 2444 while the facets formingsurface 242 meet at an apex 2411. The facets of each surface can havelinear or arcuate shapes. Moreover, the facets may be arranged toreflect the light received from the input end of the extractor indifferent angular sub-ranges. In this manner, light provided by thedifferent facets of each of the surfaces 242 and 244 is output at theoutput surfaces 246 and 248, respectively, as two intensity lobes thatcan be manipulated differently, e.g., to illuminate different targets.

FIG. 2F shows a redirecting surface 243-f where the redirecting surfaces242 and 244 are separated by a slot 245, in general a suitably formedaperture. Slot 245 corresponds to a gap in the reflective material atthe surface and allows for light to be transmitted in a forwarddirection out of the optical extractor. In general, the width of theslot 245 may vary as desired, in accordance with the desired proportionof light to be transmitted by the optical extractor.

FIG. 2G shows a redirecting surface 243-g in which surface 242 includesa slot 2455′ and surface 244 includes a slot 2455″. Such slots mayrepresent an opening in a coating providing a reflecting layer of theredirecting surface 243-g and allows transmission of at least some ofthe light received from the light guide.

For redirecting surfaces 243-f and 243-g, each slot may extend along theentire longitudinal extension of the active illumination device 200.Alternatively, redirecting surfaces may include multiple slots eachextending a fraction of the length of the device. Moreover, whileembodiments showing a single slot and two slots (in a cross-section) areillustrated, it will be appreciated that any number of slots may beincluded depending on the desired transmission properties of the opticalextractor. Furthermore, embodiments may feature additional opticalelements located at the slots to shape the transmitted light. Forexample, optical extractors may include focusing or defocusing elements,diffusing elements, and/or diffractive elements that provide additionallight shaping to the light transmitted by the slots.

In addition, the curves corresponding to each of the cross-sectionalplanes illustrated in FIGS. 2B-2G can have different shapes anddifferent discontinuities in other cross-sectional planes along thelongitudinal dimension of the active illumination device 200. Ingeneral, different cross-sections of a redirecting surface 243 can havedifferent combinations of disjoint or joined piecewise differentiablecurves.

In the examples illustrated in FIGS. 2F-2G, the active illuminationdevice 200 can be used as an active illumination device 150, wheredirect illumination corresponds to light output through the transparentportions of the redirecting surface 243-f or 243-g, and indirectillumination corresponds to light output through surfaces 246/248 of theactive illumination device 200, as described below in connection withFIGS. 3-4.

In some embodiments, it is also possible to use redirecting surfacesthat do not include slots in the reflective layer to provide both directand indirect light as shown in FIGS. 3-4. For example, rather thanproviding a highly-reflective layer on the redirecting surface, apartially-reflecting layer may instead be used (e.g., apartially-silvered surface). In this way, the redirecting surface (e.g.,as illustrated in FIGS. 2B-2E) acts as a beam splitter rather than amirror, and transmits a desired portion of incident light, whilereflecting the remaining light. In certain embodiments, additionaloptical layers may be included adjacent the partially-reflecting layerthat can further shape the transmitted light. For example, a diffusinglayer may be included. Alternatively, or additionally, a lens or lensarray may be included (e.g., such as a micro-structured film composed oflenticular lenses or prisms).

In the examples illustrated in FIGS. 2B-2E, where a highly reflectivematerial is included at the redirecting surface, light is output fromthe optical extractor 240 of the active illumination device 200 onlythrough surfaces 246/248. In this case, active illumination device 200can be used as a component of the active illumination device 150, wherethe output light is further redirected by tertiary reflectors to providedirect illumination, as described below in connection with FIGS. 5-8.

Moreover, the shape of output surfaces of the optical extractor 246 and248 can vary too, and thus, the surfaces 246 and 248 can steer and shapethe beam of light. For example, the radius of curvature of thesesurfaces can be selected so that the surfaces introduce a desired amountof convergence into the light. Aspheric surfaces can also be used.Similar properties noted above in connection with FIGS. 2B-2G regardingcontours of the redirecting surface of the extractor 243 incross-sectional planes substantially perpendicular to the longitudinaldimension of the active illumination device 200 apply to contours of theoutput surfaces of the extractor 246, 248 in such cross-sectionalplanes.

In general, choices of redirecting surfaces described in FIGS. 2B-2G mayprovide an additional degree of freedom for modifying the (direct orindirect or both) intensity distribution (e.g., illumination pattern) ofthe light output by the active illumination devices described inconnection with FIGS. 3-8. In general, two or more of the activeillumination device 200, the direct secondary reflectors, the indirectoptics, the arrangement of indirect and direct LEEs with respect to amount of an illumination device, and the first and second apexes may beiteratively modified in their spatial position and/or optical properties(spatial shape of reflective surfaces, index of refraction of solidmaterial, spectrum of emitted or guided light etc.) to provide apredetermined direct and/or indirect illumination distribution.

In general, the geometry of the elements can be established using avariety of methods. For example, the geometry can be establishedempirically. Alternatively, or additionally, the geometry can beestablished using optical simulation software, such as Lighttools™,Tracepro™, FRED™ or Zemax™, for example.

In general, luminaire modules can include other features useful fortailoring the intensity profile. For example, in some implementations,luminaire modules can include an optically diffuse material thatscatters light, thereby homogenizing the luminaire module's intensityprofile. For example, surfaces 242 and 244 can be rough or a diffuselyreflecting material, rather than a specular reflective material, can becoated on these surfaces. Accordingly, the optical interfaces atsurfaces 242 and 244 can diffusely reflect light, scattering light intobroader lobes than would be provided by similar structures that utilizespecular reflection at smooth interfaces. In some implementations, thesesurfaces can include structure that facilitates various intensitydistributions. For example, surfaces 242 and 244 can each have multipleplanar facets at differing orientations. Accordingly, each facet willreflect light into different directions. In some implementations,surfaces 242 and 244 can have structure thereon (e.g., structuralfeatures that scatter or diffract light).

In certain implementations, a light scattering material can be disposedon surfaces 246 and 248 of optical extractor 240 (e.g., surfaces 246 and248 may be rough or include a layer of a diffusely transmittingmaterial). Alternatively, or additionally, surfaces 246 and 248 need notbe surfaces having a constant radius of curvature. For example, surfaces246 and 248 can include portions having differing curvature and/or canhave structure thereon (e.g., structural features that scatter ordiffract light).

FIG. 3 shows an example of an active illumination device 300 to be usedin the illumination system 100 of FIG. 1A. In this example, the activeillumination device 300 includes a solid embodiment of the activeillumination device 200 described above in connection with FIG. 2A.Further in this example, the active illumination device 300 is supportedby a ceiling 180 through a support 108. In some implementations, theactive illumination device 300 is elongated along the y-axis(perpendicular to the page.) The active illumination device 300 includesa mount 210, one or more LEEs 212, primary optics 220 (also referred toas couplers), a light guide 230 and a solid secondary optic 240 (alsoreferred to as an optical extractor).

In this example, the mount 210 has a first surface 210 a with a normalparallel to the z-axis. The multiple LEEs 212 are operatively disposedon the first surface 210 a of the mount, such that the LEEs 212 emit,during operation, light in a first angular range with respect to thenormal to the first surface 210 a of the mount 210.

The primary optics 220 are arranged on the first surface 210 a andcoupled with the LEEs 212. The primary optics 220 are shaped to redirectlight received from the LEEs 212 in the first angular range, and toprovide the redirected light in a second angular range 252. A divergenceof the second angular range 252 is smaller than a divergence of thefirst angular range at least in the x-z plane. The light guide 230includes input and output ends. In this case, the input and output endsof the light guide 230 have substantially the same shape. The input endof the light guide 230 is coupled to the primary optics 220 to receivethe light provided by the primary optics 220 in the second angular range252. Further, in this example, the light guide 230 is shaped to guidethe light received from the primary optics 220 in the second angularrange and to provide the guided light in substantially the same secondangular range 252 with respect to the first surface 210 a of the mount210 at the output end of the light guide 230.

The solid secondary optic 240 includes an input end, a redirectingsurface 243-g opposing the input end and first and second outputsurfaces. The input end of the solid secondary optic 240 is coupled tothe output end of the light guide 230 to receive the light provided bythe light guide 230 in the second angular range 252. In this case, theredirecting surface 243-g has been described above in connection withFIG. 2G. The redirecting surface 243-g has first and second portionsthat reflect the light received at the input end of the solid secondaryoptic 240 in the second angular range 252, and provide the reflectedlight in third and fourth angular ranges with respect to the normal tothe first surface 210 a of the mount 210 towards the first and secondoutput surfaces, respectively. At least prevalent directions ofpropagation of light in the third and fourth angular ranges aredifferent from each other and from a prevalent direction of propagationof light in the second angular range 252 at least perpendicular to they-axis. Additionally, some regions of the first and second portions ofthe redirecting surface 243-g are transparent (e.g., are uncoated with areflecting layer, or have slots, apertures, etc.), such that the firstand second portions of the redirecting surface 243-g transmit (andsometime refract) the light received at the input end of the solidsecondary optic 240 in the second angular range 252, and output thetransmitted (“leaked”) and refracted light in fifth 152 and sixth 152′angular ranges with respect to the normal to the first surface 210 a ofthe mount 210, respectively, outside the first and second portions ofthe redirecting surface 243-g. Moreover, prevalent directions ofpropagation of light in the fifth 152 and sixth 152′ angular ranges aredifferent from each other and have a non-zero component parallel withthe normal to the first surface 210 a of the mount 210. Note that whentransmission (“leakage”) of light in fifth 152 and sixth 152′ angularranges occurs through apertures of planar first and second portions ofthe redirected surface 243-f or 243-g, a combination of the fifth 152and sixth 152′ angular ranges corresponds to the second angular range252 of the light received at the input end of the solid secondary optic240 adjusted (typically enlarged) by the relative refractive index.

The first output surface is shaped to refract the light provided by thefirst portion of the redirecting surface 243-g in the third angularrange as first refracted light, and to output the first refracted lightin a seventh angular range 142 with respect to the normal to the firstsurface 210 a of the mount 210 outside the first output surface of thesolid secondary optic 240. The second output surface is shaped torefract the light provided by the second portion of the redirectingsurface 243-g in the fourth angular range as second refracted light, andto output the second refracted light in an eighth angular range 142′with respect to the normal of the first surface 210 a of the mount 210outside the second output surface of the solid secondary optic 240.Moreover, prevalent directions of propagation of light in the seventh142 and eighth 142′ angular ranges are different from each other andhave a non-zero component antiparallel with the normal to the firstsurface 210 a of the mount 210.

In this manner, in some implementations, the active illumination device300 provides direct illumination (in angular ranges 152, 152′) on atarget surface located in the positive direction of the z-axis (e.g., onthe floor 190) and indirect illumination (in angular ranges 142, 142′)towards the ceiling 180. In other implementations, the activeillumination device 300 provides direct illumination (in the secondangular range 252) on the target surface located in the positivedirection of the z-axis (e.g., on the floor 190) and indirectillumination (in angular ranges 142, 142′) towards the ceiling 180.

FIG. 4 shows another example of an active illumination device 400 to beused in the illumination system 100 of FIG. 1A. In this example, theactive illumination device 400 includes a “hollow embodiment” (i.e.,embodiments that do not include a light guide or solid opticalextractor) of the luminaire module described above in connection withFIG. 2A. Further in this example, the active illumination device 400 issupported by a ceiling 180 through a support 108. In someimplementations, the active illumination device 400 is elongated alongthe y-axis (perpendicular to the page.) The active illumination device400 includes a mount 210, multiple LEEs 212, primary optics 220 and asecondary optic 440.

In this example, the mount 210 has a first surface 210 a with a normalparallel to the z-axis. The multiple LEEs 212 are operatively disposedon the first surface 210 a of the mount, such that the LEEs 212 emit,during operation, light in a first angular range with respect to thenormal to the first surface 210 a of the mount 210.

The primary optics 220 are arranged on the first surface 210 a andcoupled with the LEEs 212. The primary optics 220 are shaped to redirectlight received from the LEEs 212 in the first angular range, and toprovide the redirected light in a second angular range 252. A divergenceof the second angular range 252 is smaller than a divergence of thefirst angular range at least in the x-z plane.

The secondary optic 440 includes a redirecting surface 243-b/g. In thiscase, the redirecting surface 243-b/g has first and second portions thatare shaped as described above in connection with FIG. 2B. In addition,some regions of the first and second portions of the redirecting surface243-b/g are transparent (e.g., are uncoated with a reflecting layer, orhave slots, apertures, etc.) The first and second portions of theredirecting surface 243-b/g reflect the light received from the primaryoptics 220 in the second angular range 252, and provide the reflectedlight in third 142 and fourth 142′ angular ranges with respect to thenormal to the first surface 210 a of the mount 210, respectively. Atleast prevalent directions of propagation of light in the third 142 andfourth 142′ angular ranges are different from each other and from aprevalent direction of propagation of light in the second angular range252 at least perpendicular to the y-axis. Moreover, prevalent directionsof propagation of light in the third 142 and fourth 142′ angular rangesare different from each other and have a non-zero component antiparallelwith the normal to the first surface 210 a of the mount 210.

Additionally, the transparent regions of the first and second portionsof the redirecting surface 243-b/g transmit the light received from theprimary optics 220 in the second angular range 252, and output thetransmitted (“leaked”) light in fifth 152 and sixth 152′ angular rangeswith respect to the normal to the first surface 210 a of the mount 210,respectively. Note that in this case, a combination of the fifth 152 andsixth 152′ angular ranges corresponds to the second angular range 252 ofthe light received from the primary optics 220. Moreover, prevalentdirections of propagation of light in the fifth 152 and sixth 152′angular ranges are different from each other and have a non-zerocomponent parallel with the normal to the first surface 210 a of themount 210. Note that when transmission (“leakage”) of light in fifth 152and sixth 152′ angular ranges may occur without refraction (e.g.,through apertures of the redirected surface 243-b/g), a combination ofthe fifth 152 and sixth 152′ angular ranges corresponds to the secondangular range 252 of the light received at the secondary optic 440.

In this manner, in some implementations, the active illumination device400 provides direct illumination (in angular ranges 152, 152′) on atarget surface located in the positive direction of the z-axis (e.g., onthe floor 190) and indirect illumination (in angular ranges 142, 142′)towards the ceiling 180. In other implementations, the activeillumination device 400 provides direct illumination (in the secondangular range 252) on the target surface located in the positivedirection of the z-axis (e.g., on the floor 190) and indirectillumination (in angular ranges 142, 142′) towards the ceiling 180.

In some embodiments, active illumination devices may include additionaloptical elements in order to further tailor the provided illumination.For example, FIG. 5 shows an active illumination device 500 to be usedin the illumination system 100 which includes a mount 510 that has afirst surface 510 a with a normal parallel to the z-axis. The mountsupports a solid embodiment of the active illumination device 200(described above in connection with FIGS. 2A and 3), and tertiaryreflectors 550, 550′. Further in this example, the active illuminationdevice 500 is supported by a ceiling 180 through a support 108. In someimplementations, the components of the active illumination device 500are elongated along the y-axis (perpendicular to the page.)

The solid active illumination device 200 includes multiple LEEs 212,primary optics 220, a light guide 230 and a solid secondary optic 240.The multiple LEEs 212 are operatively disposed on the first surface 510a of the mount, such that the LEEs 212 emit, during operation, light ina first angular range with respect to the normal to the first surface210 a of the mount 210.

The primary optics 220 are arranged on the first surface 210 a andcoupled with the LEEs 212. The primary optics 220 are shaped to redirectlight received from the LEEs 212 in the first angular range, and toprovide the redirected light in a second angular range. A divergence ofthe second angular range is smaller than a divergence of the firstangular range at least in the x-z plane. The light guide 230 includesinput and output ends. In this case, the input and output ends of thelight guide 230 have substantially the same shape. The input end of thelight guide 230 is coupled to the primary optics 220 to receive thelight provided by the primary optics 220 in the second angular range.Further, the light guide 230 is shaped to guide the light received fromthe primary optics 220 in the second angular range and to provide theguided light in substantially the same second angular range with respectto the first surface 510 a of the mount 510 at the output end of thelight guide 230.

The solid secondary optic 240 includes an input end, a redirectingsurface 243-c opposing the input end, and first and second outputsurfaces. The input end of the solid secondary optic 240 is coupled tothe output end of the light guide 230 to receive the light provided bythe light guide 230 in the second angular range. In this case, theredirecting surface 243-c has been described above in connection withFIG. 2C. The redirecting surface 243-c has first and second portions,and in this case each of the portions of the redirecting surface 243-chas two facets. The first and second portions of the redirecting surface243-c reflect the light received at the input end of the solid secondaryoptic 240 in the second angular range, and provide the reflected lightin third and fourth angular ranges with respect to the normal to thefirst surface 510 a of the mount 510 towards the first and second outputsurfaces, respectively. At least prevalent directions of propagation oflight in the third and fourth angular ranges are different from eachother and from a prevalent direction of propagation of light in thesecond angular range at least perpendicular to the y-axis.

The first output surface is shaped to refract the light provided by thefirst portion of the redirecting surface 243-c in the third angularrange as first refracted light, and to output the first refracted lightin a fifth angular range (142+142 a) with respect to the normal to thefirst surface 510 a of the mount 510 outside the first output surface ofthe solid secondary optic 240. The second output surface is shaped torefract the light provided by the second portion of the redirectingsurface 243-c in the fourth angular range as second refracted light, andto output the second refracted light in a sixth angular range (142′+142b) with respect to the normal of the first surface 510 a of the mount510 outside the second output surface of the solid secondary optic 240.Prevalent directions of propagation of light in the fifth (142+142 a)and sixth (142′+142 b) angular ranges are different from each other. Inthis example, a relative orientation of facets of the redirectingsurface 243-c separates each of the fifth (142+142 a) and sixth(142′+142 b) angular ranges into portions of extracted light that can beused to form indirect and direct components of an intensity distributionassociated with the active illumination device 500. For instance, lightextracted from the solid secondary optic 240 in first 142 and second142′ angular sub-ranges of the fifth (142+142 a) and sixth (142′+142 b)angular ranges is redirected from a steeper facet of the redirectingsurface 243-c, and light extracted from the solid secondary optic 240 inthird 142 a and fourth 142 b angular sub-ranges of the fifth (142+142 a)and sixth (142′+142 b) angular ranges is redirected from a shallowerfacet of the redirecting surface 243-c.

A first tertiary reflector 550 supported on a second surface of themount 510, at least in part, faces the first output surface of the solidsecondary optic 240. The first tertiary reflector 550 is shaped toreflect at least some of the light output by the first output surface ofthe solid secondary optic 240 in the third angular sub-range 142 a asoutput light in a seventh angular range 152 with respect to the normalto the first surface 510 a of the mount 510. A second tertiary reflector550′ supported on a third surface of the mount 510, at least in part,faces the second output surface of the solid secondary optic 240. Thesecond tertiary reflector 550′ is shaped to reflect at least some of thelight output by the second output surface of the solid secondary optic240 in the fourth angular sub-range 142 b as output light in an eightangular range 152′ with respect to the normal to the first surface 510 aof the mount 510. Prevalent directions of propagation of light in theseventh 152 and eight 152′ angular ranges are different from each otherand have a non-zero component parallel with the normal to the firstsurface 510 a of the mount 510.

In this example, an extent of the first and second tertiary reflectors550, 550′ along the x-axis is configured to allow the light output infirst 142 and second 142′ angular sub-ranges to pass the first andsecond tertiary reflectors 550, 550′ without being reflected. Prevalentdirections of propagation of light in the first 142 and second 142′angular sub-ranges have a non-zero component antiparallel with thenormal to the first surface 510 a of the mount 510.

In this manner, the active illumination device 500 provides directillumination (in angular ranges 152, 152′) on a target surface locatedin the positive direction of the z-axis (e.g., on the floor 190) andindirect illumination (in angular ranges 142, 142′) towards the ceiling180.

In other implementations (not illustrated in FIG. 5), the extent of thefirst and second tertiary reflectors 550, 550′ along the x-axis isconfigured to transmit at least some of the light output by the firstoutput surface of the solid secondary optic 240 in the fifth angular(142+142 a) as output light in the seventh angular range 152 withrespect to the normal to the first surface 510 a of the mount 510, andat least some of the light output by the second output surface of thesolid secondary optic 240 in the sixth angular (142′+142 b) as outputlight in the sixth angular range 152 with respect to the normal to thefirst surface 510 a of the mount 510. In this case, the first and secondtertiary reflectors 550, 550′ may include transparent portions (e.g.,portions uncoated with reflecting coating, apertures, slots, etc.)configured to transmit at least some of the light output by the firstoutput surface of the solid secondary optic 240 in the fifth angularrange (142+142 a) and by the second output surface of the solidsecondary optic 240 in the sixth angular range (142′+142 b). In thismanner, the active illumination device 500 provides direct illumination(as light reflected by the tertiary reflectors 550, 550′ in angularranges 152, 152′) on a target surface located in the positive directionof the z-axis (e.g., on the floor 190) and indirect illumination (aslight transmitted by the tertiary reflectors 550, 550′ in angular ranges(142+142 a), (142′+142 b)) towards the ceiling 180.

FIG. 6 shows another example of an active illumination device 600 to beused in the illumination system 100 of FIG. 1A. In this example, theactive illumination device 600 includes a mount 510 that has a firstsurface 510 a with a normal parallel to the z-axis. The mount supports ahollow embodiment of the luminaire module (described above in connectionwith FIGS. 2A and 4), and tertiary reflectors 550, 550′. Further in thisexample, the active illumination device 600 is supported by a ceiling180 through a support 108. In some implementations, the components ofthe active illumination device 600 are elongated along the y-axis(perpendicular to the page.)

The hollow luminaire module includes multiple LEEs 212, primary optics220 and a secondary optic 440. The multiple LEEs 212 are operativelydisposed on the first surface 510 a of the mount 510, such that the LEEs212 emit, during operation, light in a first angular range with respectto the normal to the first surface 510 a of the mount 510.

The primary optics 220 are arranged on the first surface 510 a andcoupled with the LEEs 212. The primary optics 220 are shaped to redirectlight received from the LEEs 212 in the first angular range, and toprovide the redirected light in a second angular range. A divergence ofthe second angular range is smaller than a divergence of the firstangular range at least in the x-z plane.

The secondary optic 240 includes a redirecting surface 243-b. In thiscase, the redirecting surface 243-b has been described above inconnection with FIG. 2B. The redirecting surface 243-b has first andsecond portions, each of which has a curvilinear cross-section in thex-z plane. The first and second portions of the redirecting surface243-b reflect the light received from the primary optics 220 in thesecond angular range, and provide the reflected light in third (142+142a) and fourth (142′+142 b) angular ranges with respect to the normal tothe first surface 510 a of the mount 510, respectively. At leastprevalent directions of propagation of light in the third (142+142 a)and fourth (142′+142 b) angular ranges are different from each other andfrom a prevalent direction of propagation of light in the second angularrange at least perpendicular to the y-axis. In this example, lightreflected by the redirecting surface 243-b in first 142 and second 142′angular sub-ranges of the third (142+142 a) and fourth (142′+142 b)angular ranges is reflected from a steeper region of the redirectingsurface 243-b, and light reflected by the redirecting surface 243-b inthird 142 a and fourth 142 b angular sub-ranges of the third (142+142 a)and fourth (142′+142 b) angular ranges is redirected from a shallowerregion of the redirecting surface 243-b.

A first tertiary reflector 550 supported on a second surface of themount 510, at least in part, faces the first portion of the redirectingsurface 243-b. The first tertiary reflector 550 is shaped to reflect atleast some of the light redirected by the first portion of theredirecting surface 243-b in the third angular sub-range 142 a as outputlight in a fifth angular range 152 with respect to the normal to thefirst surface 510 a of the mount 510. A second tertiary reflector 550′supported on a third surface of the mount 510, at least in part, facesthe second portion of the redirecting surface 243-b. The second tertiaryreflector 550′ is shaped to reflect at least some of the lightredirected by the second portion of the redirecting surface 243-b in thefourth angular sub-range 142 b as output light in a sixth angular range152′ with respect to the normal to the first surface 510 a of the mount510. Prevalent directions of propagation of light in the fifth 152 andsixth 152′ angular ranges are different from each other and have anon-zero component parallel with the normal to the first surface 510 aof the mount 510.

In this example, an extent of the first and second tertiary reflectors550, 550′ along the x-axis is configured to allow the light redirectedin first 142 and second 142′ angular sub-ranges to pass the first andsecond tertiary reflectors 550, 550′ without being reflected. Prevalentdirections of propagation of light in the first 142 and second 142′angular sub-ranges have a non-zero component antiparallel with thenormal to the first surface 510 a of the mount 510.

In this manner, the active illumination device 600 provides directillumination (in angular ranges 152, 152′) on a target surface locatedin the positive direction of the z-axis (e.g., on the floor 190) andindirect illumination (in angular ranges 142, 142′) towards the ceiling180.

In other implementations (not illustrated in FIG. 6), the extent of thefirst and second tertiary reflectors 550, 550′ along the x-axis isconfigured to transmit at least some of the light reflected by the firstportion of the redirecting surface 243-b in the third angular (142+142a) as output light in the fifth angular range 152 with respect to thenormal to the first surface 510 a of the mount 510, and at least some ofthe light reflected by the second portion of the redirecting surface243-b in the fourth angular (142′+142 b) as output light in the sixthangular range 152 with respect to the normal to the first surface 510 aof the mount 510. In this case, the first and second tertiary reflectors550, 550′ include transparent portions (e.g., portions uncoated withreflecting coating, or apertures, slots, etc.) configured to transmit atleast some of the light reflected by the first portion of theredirecting surface 243-b in the third angular range (142+142 a) and bythe second portion of the redirecting surface 243-b in the fourthangular range (142′+142 b). In this manner, the active illuminationdevice 600 provides direct illumination (as light reflected by thetertiary reflectors 550, 550′ in angular ranges 152, 152′) on a targetsurface located in the positive direction of the z-axis (e.g., on thefloor 190) and indirect illumination (as light transmitted by thetertiary reflectors 550, 550′ in angular ranges (142+142 a), (142′+142b)) towards the ceiling 180.

In some implementations, the active illumination devices 150 areconfigured to allow interdependent as well as independent control of thedirect and indirect illuminations by a user, as described in detailbelow in this specification in connection with FIGS. 7-8.

FIG. 7, for example, shows an active illumination device 700 to be usedin the illumination system 100 of FIG. 1A. In this example, the activeillumination device 700 includes a mount 710 that has a first surface710 a with a normal parallel to the z-axis. The mount 710 supports adirect optical system and an indirect optical system. The direct opticalsystem includes direct LEEs 711 as part of a solid embodiment of theactive illumination device 200 (described above in connection with FIGS.2A, 3 and 5) and tertiary reflectors 550, 550′. The indirect opticalsystem includes indirect LEEs 701 a, 701 b and indirect primary optics702 a, 702 b. Further in this example, the active illumination device700 is supported by a ceiling 180 through a support 108. In someimplementations, the components of the direct and indirect opticalsystem of the active illumination device 700 are elongated along they-axis (perpendicular to the page.)

The solid active illumination device 200 includes multiple direct LEEs711, primary direct optics, a light guide and a solid secondary optic.The multiple direct LEEs 711 are operatively disposed on the firstsurface 710 a of the mount, such that the direct LEEs emit, duringoperation, light in a first direct angular range with respect to thenormal to the first surface 710 a of the mount 710.

The direct primary optics are arranged on the first surface 710 a andcoupled with the direct LEEs 711. The direct primary optics are shapedto redirect light received from the direct LEEs 711 in the first directangular range, and to provide the redirected light in a second directangular range. A divergence of the second direct angular range issmaller than a divergence of the first direct angular range at least inthe x-z plane. The light guide includes input and output ends. In thiscase, the input and output ends of the light guide have substantiallythe same shape. The input end of the light guide is coupled to thedirect primary optics to receive the light provided by the directprimary optics in the second direct angular range. Further, the lightguide is shaped to guide the light received from the direct primaryoptics in the second direct angular range and to provide the guidedlight in substantially the same second direct angular range with respectto the first surface 710 a of the mount 710 at the output end of thelight guide.

The solid secondary optic includes an input end, a redirecting surfaceopposing the input end, and first and second output surfaces. The inputend of the solid secondary optic is coupled to the output end of thelight guide to receive the light provided by the light guide in thesecond direct angular range. The redirecting surface has first andsecond portions that reflect the light received at the input end of thesolid secondary optic in the second direct angular range, and providethe reflected light in third and fourth direct angular ranges withrespect to the normal to the first surface 710 a of the mount 710towards the first and second output surfaces, respectively. At leastprevalent directions of propagation of light in the third and fourthdirect angular ranges are different from each other and from a prevalentdirection of propagation of light in the second direct angular range atleast perpendicular to the y-axis.

The first output surface is shaped to refract the light provided by thefirst portion of the redirecting surface in the third direct angularrange as first refracted light, and to output the first refracted lightin a fifth direct angular range with respect to the normal to the firstsurface 710 a of the mount 710 outside the first output surface of thesolid secondary optic. The second output surface is shaped to refractthe light provided by the second portion of the redirecting surface inthe fourth direct angular range as second refracted light, and to outputthe second refracted light in a sixth direct angular range with respectto the normal of the first surface 710 a of the mount 710 outside thesecond output surface of the solid secondary optic. Prevalent directionsof propagation of light in the fifth and sixth direct angular ranges aredifferent from each other.

A first tertiary reflector 550 supported on a second surface of themount 710, at least in part, faces the first output surface of the solidsecondary optic. The first tertiary reflector 550 is shaped to reflectat least some of the light output by the first output surface of thesolid secondary optic in the fifth direct angular range as output lightin a seventh direct angular range 152 with respect to the normal to thefirst surface 710 a of the mount 710. A second tertiary reflector 550′supported on a third surface of the mount 710, at least in part, facesthe second output surface of the solid secondary optic. The secondtertiary reflector 550′ is shaped to reflect at least some of the lightoutput by the second output surface of the solid secondary optic in thesixth direct angular range as output light in an eight direct angularrange 152′ with respect to the normal to the first surface 710 a of themount 710. Prevalent directions of propagation of light in the seventh152 and eighth 152′ direct angular ranges are different from each otherand have a non-zero component parallel with the normal to the firstsurface 710 a of the mount 710.

In this example, first indirect LEEs 701 a are operatively disposed on afourth surface of the mount 710. The first indirect LEEs 701 a emit,during operation, light in a first indirect angular range with respectto a normal to the first surface 710 a. Second indirect LEEs 701 b areoperatively disposed on a fifth surface of the mount 710, such that thefourth and fifth surfaces are oriented obliquely with respect to eachother and to the first surface 710 a. The second indirect LEEs 701 bemit, during operation, light in a second indirect angular range withrespect to a normal to the first surface 710 a. At least prevalentdirections of propagation of light in the first and second indirectangular ranges are different from each other and from a prevalentdirection of propagation of light in the first angular range at leastperpendicular to the y-axis.

A first indirect primary optic 702 a is arranged on the fourth surfaceof the mount 710 to couple with the first indirect LEEs 701 a. The firstindirect primary optic 702 a is shaped to redirect light received fromthe first indirect LEEs 701 a in the first indirect angular range, andto provide the redirected light as output light in a third indirectangular range 162′ with respect to the normal to the first surface 710a. A divergence of the third indirect angular range 162′ is smaller thana divergence of the first indirect angular range at least in a planeperpendicular to the y-axis. A second indirect primary optic 702 b isarranged on the fifth surface of the mount 710 to couple with the secondindirect LEEs 701 b. The second indirect primary optic 702 b is shapedto redirect light received from the second indirect LEEs 701 b in thesecond indirect angular range, and to provide the redirected light asoutput light in a fourth indirect angular range 162 with respect to thenormal to the first surface 710 a. A divergence of the fourth indirectangular range 162 is smaller than a divergence of the second indirectangular range at least in a plane perpendicular to the longitudinaldimension of the first surface 710 a, and prevalent directions ofpropagation of light in the third 162′ and fourth 162 indirect angularranges are different from each other and have a non-zero componentantiparallel with the normal to the first surface 710 a of the mount710.

In this manner, the active illumination device 700 provides directillumination (in angular ranges 152, 152′) on a target surface locatedin the positive direction of the z-axis (e.g., on the floor 190) andindirect illumination (in angular ranges 162, 162′) towards the ceiling180.

FIG. 8 shows a further example of an active illumination device 800 tobe used in the illumination system 100 of FIG. 1A. In this example, theactive illumination device 800 includes a mount 710 that has a firstsurface 710 a with a normal parallel to the z-axis. The mount 710supports a direct optical system and an indirect optical system. Thedirect optical system includes direct LEEs 711 as part of a hollowembodiment of the luminaire module (described above in connection withFIGS. 2A, 4 and 6) and tertiary reflectors 550, 550′. The indirectoptical system includes indirect LEEs 701 a, 701 b and indirect primaryoptics 702 a, 702 b. Further in this example, the active illuminationdevice 800 is supported by a ceiling 180 through a support 108. In someimplementations, the components of the direct and indirect opticalsystem of the active illumination device 800 are elongated along they-axis (perpendicular to the page.)

The hollow luminaire module includes multiple direct LEEs, primarydirect optics 820 and a secondary optic 840. The multiple direct LEEsare operatively disposed on the first surface 710 a of the mount, suchthat the direct LEEs emit, during operation, light in a first directangular range with respect to the normal to the first surface 710 a ofthe mount 710.

The direct primary optics 820 are arranged on the first surface 710 aand coupled with the direct LEEs 711. The direct primary optics 820 areshaped to redirect light received from the direct LEEs 711 in the firstdirect angular range, and to provide the redirected light in a seconddirect angular range. A divergence of the second direct angular range issmaller than a divergence of the first direct angular range at least inthe x-z plane.

The secondary optic 840 includes a redirecting surface. The redirectingsurface has first and second portions that reflect the light receivedfrom the direct primary optic 220 in the second direct angular range,and provide the reflected light in third and fourth direct angularranges with respect to the normal to the first surface 710 a of themount 710, respectively. At least prevalent directions of propagation oflight in the third and fourth direct angular ranges are different fromeach other and from a prevalent direction of propagation of light in thesecond direct angular range at least perpendicular to the y-axis.

A first tertiary reflector 550 supported on a second surface of themount 710, at least in part, faces the first portion of the redirectingsurface of the secondary optic 840. The first tertiary reflector 550 isshaped to reflect at least some of the light redirected by the firstportion of the redirecting surface in the third direct angular range asoutput light in a fifth direct angular range 152 with respect to thenormal to the first surface 710 a of the mount 710. A second tertiaryreflector 550′ supported on a third surface of the mount 710, at leastin part, faces the second portion of the redirecting surface. The secondtertiary reflector 550′ is shaped to reflect at least some of the lightredirected by the second portion of the redirecting surface in thefourth direct angular range as output light in a sixth direct angularrange 152′ with respect to the normal to the first surface 710 a of themount 710. Prevalent directions of propagation of light in the fifth 152and sixth 152′ direct angular ranges are different from each other andhave a non-zero component parallel with the normal to the first surface710 a of the mount 710.

In this example, first indirect LEEs 701 a are operatively disposed on afourth surface of the mount 710. The first indirect LEEs 701 a emit,during operation, light in a first indirect angular range with respectto a normal to the first surface 710 a. Second indirect LEEs 701 b areoperatively disposed on a fifth surface of the mount 710, such that thefourth and fifth surfaces are oriented obliquely with respect to eachother and to the first surface 710 a. The second indirect LEEs 701 bemit, during operation, light in a second indirect angular range withrespect to a normal to the first surface 710 a. At least prevalentdirections of propagation of light in the first and second indirectangular ranges are different from each other and from a prevalentdirection of propagation of light in the first angular range at leastperpendicular to the y-axis.

A first indirect primary optic 702 a is arranged on the fourth surfaceof the mount 710 to couple with the first indirect LEEs 701 a. The firstindirect primary optic 702 a is shaped to redirect light received fromthe first indirect LEEs 701 a in the first indirect angular range, andto provide the redirected light as output light in a third indirectangular range 162′ with respect to the normal to the first surface 710a. A divergence of the third indirect angular range 162′ is smaller thana divergence of the first indirect angular range at least in a planeperpendicular to the y-axis. A second indirect primary optic 702 b isarranged on the fifth surface of the mount 710 to couple with the secondindirect LEEs 701 b. The second indirect primary optic 702 b is shapedto redirect light received from the second indirect LEEs 701 b in thesecond indirect angular range, and to provide the redirected light asoutput light in a fourth indirect angular range 162 with respect to thenormal to the first surface 710 a. A divergence of the fourth indirectangular range 162 is smaller than a divergence of the second indirectangular range at least in a plane perpendicular to the longitudinaldimension of the first surface 710 a, and prevalent directions ofpropagation of light in the third 162′ and fourth 162 indirect angularranges are different from each other and have a non-zero componentantiparallel with the normal to the first surface 710 a of the mount710.

In this manner, the active illumination device 700 provides directillumination (in angular ranges 152, 152′) on a target surface locatedin the positive direction of the z-axis (e.g., on the floor 190) andindirect illumination (in angular ranges 162, 162′) towards the ceiling180.

(iii) Passive Illumination Devices

In general, a variety of passive illumination devices can be used in theillumination system 100 to provide desired illumination. The size,shape, and composition of the passive illumination device depends on thenature of the light the device receives from adjacent activeillumination devices and on the desired distribution of light the deviceprovides to the target area. For example, the size of the passiveillumination device depends on the spatial extent of the light from theactive illumination devices. Generally, the greater the spatial extentof the light, the larger the passive illumination device will be.Furthermore, the optical properties of the passive illumination deviceare selected to provide light having the desired distribution at thetarget area from the light received from the active illuminationdevices.

FIG. 9 shows an example of a passive illumination device 170′ thatincludes a mount 174 (e.g., a rigid support) and a redirecting optic 176attached to the mount. In this example, the redirecting optic 176 is aconvex reflector shaped to redirect, towards the target area, theindirect illumination received in the indirect angular ranges 162, 162′.The redirected light propagates to the target area in direct angularranges 172, 172′. In this manner, the passive illumination device 170′provides direct illumination of the target area. Convex redirectingoptic 176 has the effect of introducing additional divergence into thereflected light. The radius of curvature of the reflector may vary inorder to provide a desired amount of divergence into the redirectedlight. Other shapes are also possible. For example, the reflector may bean aspherical reflector. In some embodiments, the reflector can beplanar or concave. A planar reflector may serve to simply change thedirection of propagation of incidence light while a concave reflectormay decrease the divergence of reflected light or collimate or focuslight. Moreover, the redirecting optic 176 can be a reflector having acontinuous surface or a faceted surface. In some implementations, thepassive illumination device 170′ is elongated along the y-axis. Forexample, the passive illumination device 170′ may extend along they-axis the same amount as active illumination device 150.

In this example, the passive illumination device 170 is attached to theceiling 180 through a support 109. The support 109 can include wires orrods, for example, or combinations thereof. The support 109 suspends thepassive illumination device 170′ a desired amount from the ceiling. Insome implementations, however, the passive illumination device can beattached directly to the ceiling.

FIG. 10 shows another example of a passive illumination device 170″ thatcan be used in the illumination system 100. The passive illuminationdevice 170″ includes mount 174 and a redirecting optic 178 attached tothe mount. In this example, the redirecting optic 178 is a Fresnelreflector shaped to redirect, towards the target area, the indirectillumination received in the indirect angular ranges 162, 162′, asredirected light in direct angular ranges 172, 172′. In this manner, thepassive illumination device 170″ provides direct illumination of thetarget area (in the form of redirected light in the direct angularranges 172, 172′).

The preceding figures and accompanying description illustrate examplemethods, systems and devices for illumination. It will be understoodthat these methods, systems, and devices are for illustration purposesonly and that the described or similar techniques may be performed atany appropriate time, including concurrently, individually, or incombination. In addition, many of the steps in these processes may takeplace simultaneously, concurrently, and/or in different orders than asshown. Moreover, the described methods/devices may use additionalsteps/parts, fewer steps/parts, and/or different steps/parts, so long asthe methods/devices remain appropriate.

In other words, although this disclosure has been described in terms ofcertain aspects or implementations and generally associated methods,alterations and permutations of these aspects or implementations will beapparent to those skilled in the art. Accordingly, the above descriptionof example implementations does not define or constrain this disclosure.Further implementations are described in the following claims.

1-23. (canceled)
 24. An illumination system, comprising: an activeillumination device configured to output backward light in obtuse anglesrelative to a forward direction, the forward direction extending fromthe active illumination device to a target surface; and a passiveillumination device arranged to receive backward light output by theactive illumination device and redirect the received light toward thetarget surface, wherein an entirety of the active illumination deviceand an entirety of the passive illumination device are spaced apart fromeach other in all directions perpendicular to the forward direction. 25.The illumination system of claim 24, wherein the active illuminationdevice is configured further to output forward light in acute anglesrelative to the forward direction.
 26. The illumination system of claim25, wherein the forward light from the active illumination deviceoverlaps with the redirected light from the passive illumination deviceon the target surface.
 27. The illumination system of claim 25, whereinthe active illumination device includes a refractive optic configured toprovide the backward light and the forward light from light receivedfrom light-emitting diodes.
 28. The illumination system of claim 25,wherein the active illumination device is configured to output theforward light with a batwing light distribution.
 29. The illuminationsystem of claim 24, wherein the forward direction is perpendicular to aceiling.
 30. The illumination system of claim 24, wherein the activeillumination device is mounted to a ceiling.
 31. The illumination systemof claim 30, wherein the passive illumination device is mounted to theceiling.
 32. The illumination system of claim 24, wherein the active andpassive illumination device have elongate extensions along a directionperpendicular to the forward direction.
 33. The illumination system ofclaim 24, wherein the active illumination device includes light-emittingdiodes (LEDs) and an optical system configured to provide the backwardlight.
 34. The illumination system of claim 33, wherein the LEDs arearranged to emit light in acute angles relative to the forwarddirection.
 35. The illumination system of claim 24, wherein the passiveillumination device comprises a reflector.
 36. The illumination systemof claim 24, wherein the passive illumination device is configured toredirect light received from multiple active illumination devices towardthe target surface.
 37. The illumination system of claim 24, wherein thepassive illumination device is configured to provide the redirectedlight with a batwing light distribution.